N6-Cyclohexyl[3H]adenosine ([3H]CHA) and 1,3-diethyl-8-[3H]phenylxanthine ([3H]DPX) bind to adenosine receptors in brain membranes. The agonist [3H]CHA has high affinity in both bovine and guinea pig brain (Kd, 0.7 nM and 6 nM, respectively). [3H]CHA binding kinetics are slow (dissociation t1/2; 60 min); binding is much higher at 25°C than at 0°C and is inhibited by guanine nucleotides. Potencies of nucleosides and xanthines in competing for [3H]CHA sites indicate that specific binding is entirely to A1 adenosine receptors. In bovine brain, the antagonist [3H]DPX exhibits high-affinity binding (Kd, 5 nM) to the same A1 receptors that bind [3H]CHA. Binding kinetics are rapid (dissociation t1/2, 1 min), and binding is moderately higher at 0°C than at 25°C. In guinea pig brain, [3H]DPX binding has only moderate affinity (Kd, 50 nM), and about 60% of specific binding is to sites that resemble A2 adenosine receptors.
|Original language||English (US)|
|Number of pages||5|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|Issue number||9 II|
|State||Published - 1980|
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